Saunas provided with an electric sauna stove and intended to be used all the year round are very often provided with an additional heating system in order to maintain a normal room temperature in the sauna room when it is not heated for bathing. The sauna room is conventionally heated by similar methods as the other parts of the building. A radiator with water circulation is a usual solution for the heating of a sauna room. In electrically heated buildings, the sauna room can be heated either by means of electric heaters specially designed for moist rooms or by means of floor heating which may be operated electrically or by means of warm circulation water. In any case, the heating of the sauna room to room temperature usually requires separate special arrangements which always bring about material and installation costs to some extent.